Eruptive style and flow dynamics of the pyroclastic density currents related to the Holocene Cerro Blanco eruption (Southern Puna plateau, Argentina)

BÁEZ, W.; BUSTOS, E.; CHIODI, A.; RECKZIEGEL, F.; ARNOSIO, M.; GIORDANO, G.; VIRAMONTE, J.G.; SAMPIETRO-VATTUONE, M. M.; PEÑA-MONNÉ, J. L.

JOURNAL OF SOUTH AMERICAN EARTH SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2020

0895-9811

Large caldera forming eruptions are relatively uncommon in the geological record, however have the potential to produce profound regional impacts in the environment, topography, drainage, and even could perturb the global climate. Despite the significant effort in the scientific community to better understand the caldera forming eruptions, volcanologists are still unable to fully explain its complex dynamics. Recent works identified the source of one of largest Holocene eruptions in the Central Andes, the 4 ka, VEI 7, Cerro Blanco eruption. This caldera forming eruption forms part of the evolution of the youngest caldera complexes in the Southern Central Andes, the Pleistocene-Holocene Cerro Blanco Volcanic Complex. Nevertheless, the published works do not fully characterize the dynamics of the Cerro Blanco eruption. This paper presents the first detailed facies analysis and architecture reconstruction of the ignimbrites related to the Holocene Cerro Blanco eruption. In addition, the eruptive sequence of the Holocene Cerro Blanco caldera‐forming eruption, highlighting the flow dynamic of the related PDCs, is discussed. A contemporaneous convective and collapsing eruptive dynamics was established and sustained throughout most of the eruption. Towards the end of the eruption, instabilities of the column occurred probably in response to the climax of a protracted incremental caldera collapse. This eruptive sequence is similar to those observed in well‐documented small collapse calderas like Cerobuco and Pinatubo. The PDCs related to the Cerro Blanco eruption were mainly inertia‐dominated. However, the channelization of parental PDCs into deep valleys allowing the flow transformation toward a forced convection‐dominated. In addition, the topographic constriction of the valleys enhances the sedimentation rate producing regressive bed forms and ultimately the avulsion of the main path of the PDCs producing the flood of secondary valleys.